scientific point of view. Continental water accounts for only 2.6% of the Earth's water, the
rest being made up of seas and oceans. Of this volume, 98% consists of sterile water, in the
form of glaciers and underground water, leaving only the water of rivers, lakes, and ponds
as shelter for living organisms- barely 2% of the total volume of Continental water
TEMPERATURE
An important parameter for aquatic life,
the temperature regulates the growth of
animals and plants and exerts an influence
not only on oxygen levels but also on
many other factors.
Whereas mammals have a regulated and
practically stable internal temperature,
that of fish and other aquarium creatures
varies according to the temperature
of the water around them. They
can survive only at certain temperatures
and some species are more sensitive than
others to variations in this parameter.
The temperatures of fresh tropical waters,
ranging from 20 to 30°C, are characterized
by less significant variations than those
found in temperate regions. In some
places the shade provided by the tropical
forest cools the water, while in calm water
the temperature goes up under the direct
influence of the sunlight.
The mean temperature most often recommended
for aquariums is 25°C, and variations
of 1 or 2° are of little consequence.
Fish are even capable of withstanding
even more significant variations for brief
periods (under 24 hours). On the other
hand, their metabolism (i.e. their general
bodily functioning) is in danger of serious
disturbance over any longer periods, and
An important parameter for aquatic life,
the temperature regulates the growth of
animals and plants and exerts an influence
not only on oxygen levels but also on
many other factors.
Whereas mammals have a regulated and
practically stable internal temperature,
that of fish and other aquarium creatures
varies according to the temperature
of the water around them. They
can survive only at certain temperatures
and some species are more sensitive than
others to variations in this parameter.
The temperatures of fresh tropical waters,
ranging from 20 to 30°C, are characterized
by less significant variations than those
found in temperate regions. In some
places the shade provided by the tropical
forest cools the water, while in calm water
the temperature goes up under the direct
influence of the sunlight.
The mean temperature most often recommended
for aquariums is 25°C, and variations
of 1 or 2° are of little consequence.
Fish are even capable of withstanding
even more significant variations for brief
periods (under 24 hours). On the other
hand, their metabolism (i.e. their general
bodily functioning) is in danger of serious
disturbance over any longer periods, and
be noted that excessively low temperatures
sometimes favor the development of
certain diseases.
sometimes favor the development of
certain diseases.
OXYGEN AND CARBON
DIOXIDE
Since air contains around 20% oxygen,
even the most oxygenated water rarely
contains more than 1% dissolved oxygen.
Fish have special organs - branchiae -
which allow them to extract most of this
(see Anatomy and Biology, page 42).
Oxygen contributes, in
addition, to the respiration
not only of
plants but also of
organisms which are
invisible to the naked
eye and often forgot
DIOXIDE
Since air contains around 20% oxygen,
even the most oxygenated water rarely
contains more than 1% dissolved oxygen.
Fish have special organs - branchiae -
which allow them to extract most of this
(see Anatomy and Biology, page 42).
Oxygen contributes, in
addition, to the respiration
not only of
plants but also of
organisms which are
invisible to the naked
eye and often forgot
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